Generation of spin waves by fs-laser pulses in transparent magnetic films: Role of the laser beam diameter

Abstract

Magnetostatic spin waves (MSWs) in magnetic dielectrics are perspective candidates for various applications including data processing, spin wave logic and quantum information. They can propagate hundreds of microns, some have nonreciprocal character and can be localized near the film interfaces. Excitation of MSWs by fs-laser pulses is beneficial since it provides local excitation and tunability. We demonstrate a method for the optical pumping of MSWs due to the inverse Faraday effect in magnetic dielectrics. Its essence is in the excitation with a nonuniform distribution of the optical power through the film depth and in optimization of the pump beam size. Propagation of the spin waves is demonstrated by detecting the magnetization dynamics tens microns away from the excitation spot. Variation of the pump beam diameter allows tuning between different types of the excited spin waves.